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<div class="titlepage"><div><div><h3 class="title">
<a name="odtone.extensions.remote_discovery"></a><a class="link" href="remote_discovery.html" title="Remote discovery">Remote discovery</a>
</h3></div></div></div>
<div class="toc"><dl><dt><span class="section"><a href="remote_discovery.html#odtone.extensions.remote_discovery.scenarios">Scenarios</a></span></dt></dl></div>
<p>
        The remote discovery mechanisms involve the discovery of peer MIHFs and its
        capabilities. This is known as MIHF discovery and it can be achieved by using
        L2 or L3 discovery mechanisms. It allows a MN to discover 802.21-enabled
        network entities and vice-versa, as well as a network entity to discover
        each other. In addition, by combining it with the MIH Capability Discover
        procedure, it is possible to find out the capabilities of the discovered
        entities, i.e., the services provided by them.
      </p>
<p>
        The ODTONE implementation provides L3 mechanisms which enable the remote
        discovery. It can be achieved by using the MIH Capability Discover procedure
        defined in the IEEE 802.21 standard and/or mechanisms that involve using
        DHCP and DNS services. Compared with the standard architecture of the IEEE
        802.21, the node has two new components: DHCP and/or DNS users. These are
        seen as MIH-enabled entities of the upper layers (i.e., MIH-Users) with which
        the MIHF interacts to request the discovery of available PoS. The DNS-User
        and the DHCP-User are then responsible for directly communicate with the
        respective server, in order to discover PoS entities and to obtain associated
        transport information.
      </p>
<p>
        <span class="inlinemediaobject"><img src="../.././images/l3_arch.png" alt="l3_arch"></span>
      </p>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
          The DNS-User and DHCP-User are working only for Linux environment. However,
          you can implement your own discovery entities with guidelines defined as
          follows.
        </p></td></tr>
</table></div>
<p>
        The MIH protocol does not support the necessary mechanisms to carry the information
        about the discovered entities. Therefore, a new optional TLV type was created
        and added to the MIH_Capability_Discover messages of the base ODTONE implementation.
        Consequently, a new data type was defined as well.
      </p>
<p>
        <span class="inlinemediaobject"><img src="../.././images/mos_dscv.png" alt="mos_dscv"></span>
      </p>
<p>
        The MOS_DSCV data type carries the discovered PoS divided by service type.
        Each PoS is identified by an instance of the MOS_INFO data type, which carries
        information about its ID, IP address and listening port.
      </p>
<p>
        The L3 discovery mechanisms can be enabled by configuring in the MIHF the
        list of discovery entities. The order by which they are configured defines
        the order by which the entities will be requested for discovering PoS. For
        example, if no entity is configured with discovery role, the discovery mechanisms
        will not be enable and therefore, the discovery mechanisms are the default
        ones, i.e., it is only possible to discover entities by multicasting MIH
        Capability Discover messages as defined in the IEEE 802.21 standard. Otherwise,
        the discovery mechanisms are enabled and, upon the receiving of a discovery
        request, the MIHF invokes the first discovery entity configured. By receiving
        the discovery results, the MIHF checks if all necessary information about
        the PoS was discovered and, based on that, decides to complement it with
        other discover mechanism or to initiate the MIH Capability exchange procedure.
      </p>
<p>
        The discovery entities retrieve the discovered information to the MIHF divided
        by services, i.e., for each service the MIHF receives a list of available
        PoS, which are individually requested for its capabilities. However, with
        this approach, if a given PoS provides more than one service it appears in
        more than one list and therefore, it is requested more than once for its
        capabilities. To avoid this repetition the MIHF tracks the requested PoS
        and, if it detects a repeated one it drops the request.
      </p>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="odtone.extensions.remote_discovery.scenarios"></a><a class="link" href="remote_discovery.html#odtone.extensions.remote_discovery.scenarios" title="Scenarios">Scenarios</a>
</h4></div></div></div>
<div class="toc"><dl>
<dt><span class="section"><a href="remote_discovery.html#odtone.extensions.remote_discovery.scenarios.dhcp">DHCP</a></span></dt>
<dt><span class="section"><a href="remote_discovery.html#odtone.extensions.remote_discovery.scenarios.dhcp_bootstrap">DHCP
          bootstrap</a></span></dt>
<dt><span class="section"><a href="remote_discovery.html#odtone.extensions.remote_discovery.scenarios.dns">DNS</a></span></dt>
<dt><span class="section"><a href="remote_discovery.html#odtone.extensions.remote_discovery.scenarios.dhcp___dns">DHCP
          + DNS</a></span></dt>
<dt><span class="section"><a href="remote_discovery.html#odtone.extensions.remote_discovery.scenarios.dhcp_bootstrap___dns">DHCP
          bootstrap + DNS</a></span></dt>
</dl></div>
<p>
          The following figures represents the discovery scenarios using the DNS
          and DHCP services provided by ODTONE.
        </p>
<div class="section">
<div class="titlepage"><div><div><h5 class="title">
<a name="odtone.extensions.remote_discovery.scenarios.dhcp"></a><a class="link" href="remote_discovery.html#odtone.extensions.remote_discovery.scenarios.dhcp" title="DHCP">DHCP</a>
</h5></div></div></div>
<p>
            <span class="inlinemediaobject"><img src="../.././images/dhcp_disc.png" alt="dhcp_disc"></span>
          </p>
</div>
<div class="section">
<div class="titlepage"><div><div><h5 class="title">
<a name="odtone.extensions.remote_discovery.scenarios.dhcp_bootstrap"></a><a class="link" href="remote_discovery.html#odtone.extensions.remote_discovery.scenarios.dhcp_bootstrap" title="DHCP bootstrap">DHCP
          bootstrap</a>
</h5></div></div></div>
<p>
            <span class="inlinemediaobject"><img src="../.././images/dhcp_boot_disc.png" alt="dhcp_boot_disc"></span>
          </p>
</div>
<div class="section">
<div class="titlepage"><div><div><h5 class="title">
<a name="odtone.extensions.remote_discovery.scenarios.dns"></a><a class="link" href="remote_discovery.html#odtone.extensions.remote_discovery.scenarios.dns" title="DNS">DNS</a>
</h5></div></div></div>
<p>
            <span class="inlinemediaobject"><img src="../.././images/dns_disc.png" alt="dns_disc"></span>
          </p>
</div>
<div class="section">
<div class="titlepage"><div><div><h5 class="title">
<a name="odtone.extensions.remote_discovery.scenarios.dhcp___dns"></a><a class="link" href="remote_discovery.html#odtone.extensions.remote_discovery.scenarios.dhcp___dns" title="DHCP + DNS">DHCP
          + DNS</a>
</h5></div></div></div>
<p>
            <span class="inlinemediaobject"><img src="../.././images/dhcp_dns_disc.png" alt="dhcp_dns_disc"></span>
          </p>
</div>
<div class="section">
<div class="titlepage"><div><div><h5 class="title">
<a name="odtone.extensions.remote_discovery.scenarios.dhcp_bootstrap___dns"></a><a class="link" href="remote_discovery.html#odtone.extensions.remote_discovery.scenarios.dhcp_bootstrap___dns" title="DHCP bootstrap + DNS">DHCP
          bootstrap + DNS</a>
</h5></div></div></div>
<p>
            <span class="inlinemediaobject"><img src="../.././images/dhcp_boot_dns_disc.png" alt="dhcp_boot_dns_disc"></span>
          </p>
</div>
</div>
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      Aveiro<br>Copyright &#169; 2009-2012 Instituto
      de Telecomunica&#231;&#245;es - P&#243;lo Aveiro<p>
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